Dependence of Hot Electron Transfer on Surface Coverage and Adsorbate Species at Semiconductor-Molecule Hybrid Interfaces

Developing a molecular-level understanding of how one could enhance hot electron transfer (HET) at semiconductor-molecule hybrid interfaces is central to advancing various future technologies. Using first-principles simulations, we investigate how surface coverage and adsorbate species influence HET at semiconductor-molecule interfaces. Counterintuitively, increasing surface coverage was found to suppress HET because nonadiabatic couplings (NACs) at the interface are noticeably altered by the increased delocalization of hot electron accepting states. Adsorbate species itself is an important factor in HET not simply because of energy levels, but because the transfer is quite sensitive to NACs. Our work shows that relatively minor variations of the NACs could lead to significant changes in the HET characteristics. Developing a “design principle” at a molecular level for enhancing HET remains a great challenge, and our work shows that controlling NACs must be part of such a design principle, in addition to the energy level alignment.